Authors' Affiliations: Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Mayo Clinic Cancer Center, Mayo Clinic, Rochester, Minnesota; and Paracelsus Medical University, Salzburg, Austria.
Cancer Res. 2014 May 1;74(9):2545-54. doi: 10.1158/0008-5472.CAN-13-2482. Epub 2014 Mar 19.
Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme of the uracil catabolic pathway, being critically important for inactivation of the commonly prescribed anti-cancer drug 5-fluorouracil (5-FU). DPD impairment leads to increased exposure to 5-FU and, in turn, increased anabolism of 5-FU to cytotoxic nucleotides, resulting in more severe clinical adverse effects. Numerous variants within the gene coding for DPD, DPYD, have been described, although only a few have been demonstrated to reduce DPD enzyme activity. To identify DPYD variants that alter enzyme function, we expressed 80 protein-coding variants in an isogenic mammalian system and measured their capacities to convert 5-FU to dihydro-fluorouracil, the product of DPD catabolism. The M166V, E828K, K861R, and P1023T variants exhibited significantly higher enzyme activity than wild-type DPD (120%, P = 0.025; 116%, P = 0.049; 130%, P = 0.0077; 138%, P = 0.048, respectively). Consistent with clinical association studies of 5-FU toxicity, the D949V substitution reduced enzyme activity by 41% (P = 0.0031). Enzyme activity was also significantly reduced for 30 additional variants, 19 of which had <25% activity. None of those 30 variants have been previously reported to associate with 5-FU toxicity in clinical association studies, which have been conducted primarily in populations of European ancestry. Using publicly available genotype databases, we confirmed the rarity of these variants in European populations but showed that they are detected at appreciable frequencies in other populations. These data strongly suggest that testing for the reported deficient DPYD variations could dramatically improve predictive genetic tests for 5-FU sensitivity, especially in individuals of non-European descent.
二氢嘧啶脱氢酶(DPD)是尿嘧啶分解代谢途径的初始限速酶,对于通常被处方的抗癌药物 5-氟尿嘧啶(5-FU)的失活至关重要。DPD 功能障碍会导致 5-FU 暴露增加,进而增加 5-FU 的合成,形成细胞毒性核苷酸,导致更严重的临床不良反应。虽然已经描述了 DPYD 基因编码的许多变体,但只有少数被证明会降低 DPD 酶活性。为了确定改变酶功能的 DPYD 变体,我们在同基因哺乳动物系统中表达了 80 种蛋白质编码变体,并测量了它们将 5-FU 转化为 DPD 分解代谢产物二氢氟尿嘧啶的能力。M166V、E828K、K861R 和 P1023T 变体的酶活性显著高于野生型 DPD(分别为 120%,P=0.025;116%,P=0.049;130%,P=0.0077;138%,P=0.048)。与 5-FU 毒性的临床关联研究一致,D949V 取代使酶活性降低了 41%(P=0.0031)。另外 30 种变体的酶活性也显著降低,其中 19 种的活性<25%。在之前的临床关联研究中,这些 30 种变体中没有一种与 5-FU 毒性相关,这些研究主要在欧洲血统的人群中进行。使用公开的基因型数据库,我们证实了这些变体在欧洲人群中的罕见性,但表明它们在其他人群中的检测频率相当高。这些数据强烈表明,对报告的缺陷 DPYD 变体进行检测可以极大地改善 5-FU 敏感性的预测性遗传检测,尤其是在非欧洲血统的个体中。